1. Field of the Invention
This invention relates to a hermetic ground pin assembly for making an electrical connection between a hermetically sealed enclosure and an external circuit.
2. Description of the Related Art
Various devices are well known for conducting an electrical signal. One type of application for signal conduction that is very demanding is in the field of implantable electronic medical devices such as pacemakers, heart pumps and implantable defibrillators. These electronic packages must be of the highest reliability and corrosion resistance as any failure can have potentially lethal consequences. The electronics are hermetically sealed within a case typically made from titanium. The case needs to be grounded to protect the circuitry inside from electromagnetic transients and electrostatic discharge. At the same time, the circuitry inside the case must be electrically isolated from the case and yet be connectable to external circuits such as a battery or signal pins.
In order to insure reliable connections gold plated pins and/or terminals are used. The plating is done after any high temperature processing. Subjecting the plating to high temperatures will destroy the integrity of the plating. Unfortunately, apart from the high cost of gold plating, the case cannot be electroplated due to physiological compatibility problems during contact with human tissue. Therefore, the. case cannot be connected directly to the electrical connectors for electroplating. In prior art designs, a ceramic insert was used to isolate the pins from the case for electroplating. Other methods then had to be employed such as special glass to metals seals around a wire to provide a ground connection after the rest of the assembly was completed. A current unmet need exists for a reliable, low cost, simple and robust hermetic ground pin assembly for making an electrical connection between a hermetically sealed enclosure and an external circuit that allow other terminals to be electroplated and the electronic enclosure to be physiologically compatible with human tissue.
3. Related Art
Examples of patents that are related to the present invention are as follows, and each patent is herein incorporated by reference for the supporting teachings:
U.S. Pat. Ser. No. 5,871,513 is a centerless ground feedthrough pin for an electrical power source in an implantable medical device.
The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging the applicant""s acknowledged duty of candor in disclosing information which may be pertinent in the examination of this application. It is respectfully stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, the applicants claimed invention.
It is a feature of the invention to provide a hermetic ground pin assembly for making an electrical connection between a hermetically sealed enclosure and an external circuit.
An additional feature of the invention is to provide a hermetic ground pin assembly for making an electrical path that includes a case or a case having an aperture therethrough and a plug located within the aperture. A low temperature braze alloy is located between the plug and the case for affixing the plug within the aperture. One or more pins are attached to the plug. A high temperature braze alloy is located between the plug and the outer pin for affixing the pin to the plug.
The invention resides not in any one of these features per se, but rather in the particular combination of all of them herein disclosed and claimed and it is distinguished from the prior art in this particular combination of all of its structures for the functions specified. Other features of the present invention will become more clear from the following detailed description of the invention, taken in conjunction with the accompanying drawings and claims, or may be learned by the practice of the invention.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. Those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.